Located at the growing tip of stems, shoot apical meristems (SAMs) are actively dividing, embryonic tissues responsible for all the aerial organs in plants. It is crucial for plants to achieve a balance between cell division and cell differentiation to maintain a functional meristem. In Arabidopsis, this balance is regulated by the CLAVATA (CLV) genes. Single loss-of-function mutations of the CLVgenes result in a progressive enlargement of shoot and floral meristems. CLV1 encodes a receptor-like kinase. CLV3 encodes a small extracellular protein and appears to be a ligand of CLV1. CLV2, a receptor-like protein, may form heterodimer with CLV1. The overall project of this proposal is to examine the hypothesis that the CLV1 signaling cascade controls the proliferation and differentiation of stem cells within the SAM in Arabidopsis. To understand in molecular detail how the receptor-like kinase CLV1 functions as a key element to maintain a functional SAM, I propose to determine if CLV1 functions as a receptor at the plasma membrane; to determine the immediate and long-term effects of CLV1 on both cell division patterning and meristematic reorganization; and to identify signaling components within the CLV1 signaling pathway. [unreadable] [unreadable]